Updated R docs and error message to reflect recent updates. (mlflow#1709

)

Documents newly added environment variables pointing to python and mlflow executable in R client.

mlflow/R/mlflow/R/install.R

@@ -20,18 +20,26 @@ mlflow_maybe_create_conda_env <- function() {
 
 #' Install MLflow
 #'
-#' Installs auxiliary dependencies of MLflow (e.g. the MLflow CLI). As a one-time setup step, you
-#' must run install_mlflow() to install these dependencies before calling other MLflow APIs.
+#' Installs auxiliary dependencies of MLflow (e.g. the MLflow CLI). As a
+#' one-time setup step, you must run install_mlflow() to install these
+#' dependencies before calling other MLflow APIs.
 #'
 #' install_mlflow() requires Python and Conda to be installed.
 #' See \url{https://www.python.org/getit/} and \url{https://docs.conda.io/projects/conda/en/latest/user-guide/install/}.
 #'
+#' Alternatively, you can set MLFLOW_PYTHON_BIN and MLFLOW_BIN environment variables
+#' instead. MLFLOW_PYTHON_BIN should poitn to python executable and MLFLOW_BIN to mlflow cli
+#' executable. These variables allow you to use custom mlflow installation. Note that there may be
+#' some compatibility issues if the custom mlflow version does not match the version of the R
+#' package.
+#'
 #' @examples
 #' \dontrun{
 #' library(mlflow)
 #' install_mlflow()
 #' }
 #'
+#'
 #' @importFrom reticulate conda_install conda_create conda_list
 #' @export
 install_mlflow <- function() {

mlflow/R/mlflow/R/python.R

@@ -9,7 +9,8 @@ get_python_bin <- function() {
   envs <- conda_list(conda = conda)
   mlflow_env <- envs[envs$name == mlflow_conda_env_name(), ]
   if (nrow(mlflow_env) == 0) {
-    stop("MLflow not configured, please run install_mlflow().")
+    stop(paste("MLflow not configured, please run install_mlflow() or ",
+               "set MLFLOW_PYTHON_BIN and MLFLOW_BIN environment variables.", sep = ""))
   }
   mlflow_env$python
 }